Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations present, the description carries the full burden and does it well: it discloses authentication requirements, payment alternatives, the output fields, the supported timeframe range, maximum candle count, and the fact that candles are returned newest last. This goes well beyond what the schema or annotations alone would provide.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The second sentence is dense and informative, covering what the tool returns and its constraints in one compact line. The first sentence is longer and terminology-heavy, describing payment methods, which is useful but slightly distracts from the core purpose and delays the functional description.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the low complexity of three parameters and the presence of an output schema, the description is mostly complete: it covers authentication, supported chains, timeframes, candle fields, limit cap, and ordering. The main gaps are the timeframe count mismatch with the schema enum and the unknown default value for the optional limit parameter.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate. It partially does: 'up to 500 candles' clarifies the limit semantics and the timeframe range is given, while the chain parameter is left to the enum. However, the description says 'fourteen timeframes' while the enum appears to list thirteen values, and the optional limit parameter's default or exact behavior is not specified.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool returns price history: open, high, low, close, volume, and trade count per candle for a single chain and chosen timeframe. It is more specific and valuable than the tool name alone, but it does not explicitly distinguish itself from the sibling 'prices' tool.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The intended use is implied: you would call this when you need historical OHLCV candle data, up to 500 candles, for a supported chain. However, it gives no explicit guidance about when to prefer this tool over alternatives or when not to use it.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.